London: Britain`s capital city braced for travel chaos on Wednesday with a planned London Underground strike expected to be the worst in years, after talks to avert the 24 hour walkout broke down.

Almost 20,000 staff of the rail network known as the "Tube", belonging to four different unions, are due to leave their posts in a dispute over pay and plans to run an all-night service on weekends from September.

The walkout is set to cause chaos for millions of travellers and bring the world`s oldest subway system to a halt from 17:30 GMT Wednesday, with "no Tube service at all on Thursday", according to Transport for London.

Disruption is expected to continue into Friday, and British media described the strike as set to be the worst since 2002.

A last-minute offer failed to clinch a deal between London Underground and The Rail, Maritime and Transport union (RMT), Aslef, Transport Salaried Staffs Association and Unite.

London Underground said the "final" offer included an average salary rise of 2 percent, salary rises in line with retail inflation for two years and a bonus of £2,000 ($3,010) for drivers on the new all-night services.

"None of the unions responded to the offer," said London Underground managing director Mike Brown.

"All we have heard is a series of speeches from trade union leaders, condemning us for communicating with our staff."

Union leaders in turn accused London Underground management of producing the proposal too late and failing to convince negotiators that safety, fairness and a balance between work and life would be protected.

"The responsibility for this strike and the disruption that it will cause rests squarely with London Underground management," said Finn Brennan, Tube organiser for the Aslef union.

"They squandered the window of opportunity to resolve this dispute by refusing to move their position in the slightest for three months and then demanding that all four trade unions accept an offer in one afternoon."

The dispute comes amid resentment over hundreds of job cuts and the closure of ticket offices on the Tube network, and an increase in ticket machines.

Transport for London argues that running Tube services 24 hours a day on weekends would support jobs, boost the economy and keep the capital in line with other global cities with 24 hour train services like New York or Berlin.

The all-night service is due to begin on September 12, and will run on Fridays and Saturdays on the Jubilee, Victoria, and most of the Central, Northern and Piccadilly underground lines.